What is the farthest distance you could comunicate using a telegraph?

Electrical tapping signals that are transmitted via electrical wire can travel as far as the wire goes. Early telegraph communications traveled 40 to 50 miles on low speed telegraph wires. With repeaters installed in the wiring to boost the signal, there is no limit in distance.

I doubt there are many telegraph systems operating today.

It is interesting to consider that Morse Code, or the spelling out of Words in long and short audio signals, has similarities to digital technology. Digital signals are spelled out like the Words of Morse code using binary coding-combinations of 1's and 0's to create the message. The telegraph office would write out the message by interpreting the dots and dashes of Morse code. The receptor for digital signals interprets the binary code to produce an audio or visual message.